Cherokee
tips cracking? We'll bet they are, even though we haven't seen
your particular aircraft. If you own a Cherokee taper wing
PA-28 151 to 236, that's more than a couple of years old, there's
a good chance your wing and stabilator tips are cracking.

How did we know? Simple. Your present tips are probably made
of a material called Royalite-basically an ABS styrene plastic.
Royalite is a good material for forming parts, as it can be
vacuum molded quite easily and inexpensively. It produces a
part that is very flexible and form fitting. The only problem
is it isn't an exterior plastic!

Royalite is very susceptible to cracking, especially in harsh
environments, i.e., areas with hot summers and cold winters.
It has relatively low tensile and shear strength. (This explains
the cracks emanating from your mounting screw holes.) It was
really designed for use on interior parts, like trims and moldings.

Met-Co Tips are constructed of hand laid-up fiberglass. Fiberglass
is highly resistant to any type of chemical action. (Remember
they make boat hulls from this stuff.) It will not age or corrode.
Fiberglass is extremely strong, it has great impact strength,
yet is flexible enough to be molded into any contour. It has
the same strength as mild steel but twice the torsional flexibility.

Finally, Royalite is not repairable. Many try to repair or
patch Royalite with-yeah, you guessed it-fiberglass! Fiberglass
is easily repaired if damaged (say by an errant fuel truck).
So, in the battle between fiberglass and plastic-bet on the
glass!